1 /*

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     3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

     4  *

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     6  * under the terms of the GNU General Public License version 2 only, as

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    10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

    11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

    12  * version 2 for more details (a copy is included in the LICENSE file that

    13  * accompanied this code).

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    24 

    25 #ifndef SHARE_GC_CMS_COMPACTIBLEFREELISTSPACE_HPP

    26 #define SHARE_GC_CMS_COMPACTIBLEFREELISTSPACE_HPP

    27 

    28 #include "gc/cms/adaptiveFreeList.hpp"

    29 #include "gc/cms/promotionInfo.hpp"

    30 #include "gc/shared/blockOffsetTable.hpp"

    31 #include "gc/shared/cardTable.hpp"

    32 #include "gc/shared/space.hpp"

    33 #include "logging/log.hpp"

    34 #include "memory/binaryTreeDictionary.hpp"

    35 #include "memory/freeList.hpp"

    36 

    37 // Classes in support of keeping track of promotions into a non-Contiguous

    38 // space, in this case a CompactibleFreeListSpace.

    39 

    40 // Forward declarations

    41 class CMSCollector;

    42 class CompactibleFreeListSpace;

    43 class ConcurrentMarkSweepGeneration;

    44 class BlkClosure;

    45 class BlkClosureCareful;

    46 class FreeChunk;

    47 class UpwardsObjectClosure;

    48 class ObjectClosureCareful;

    49 class Klass;

    50 

    51 class AFLBinaryTreeDictionary : public BinaryTreeDictionary<FreeChunk, AdaptiveFreeList<FreeChunk> > {

    52  public:

    53   AFLBinaryTreeDictionary(MemRegion mr)

    54       : BinaryTreeDictionary<FreeChunk, AdaptiveFreeList<FreeChunk> >(mr) {}

    55 

    56   // Find the list with size "size" in the binary tree and update

    57   // the statistics in the list according to "split" (chunk was

    58   // split or coalesce) and "birth" (chunk was added or removed).

    59   void       dict_census_update(size_t size, bool split, bool birth);

    60   // Return true if the dictionary is overpopulated (more chunks of

    61   // this size than desired) for size "size".

    62   bool       coal_dict_over_populated(size_t size);

    63   // Methods called at the beginning of a sweep to prepare the

    64   // statistics for the sweep.

    65   void       begin_sweep_dict_census(double coalSurplusPercent,

    66                                      float inter_sweep_current,

    67                                      float inter_sweep_estimate,

    68                                      float intra_sweep_estimate);

    69   // Methods called after the end of a sweep to modify the

    70   // statistics for the sweep.

    71   void       end_sweep_dict_census(double splitSurplusPercent);

    72   // Accessors for statistics

    73   void       set_tree_surplus(double splitSurplusPercent);

    74   void       set_tree_hints(void);

    75   // Reset statistics for all the lists in the tree.

    76   void       clear_tree_census(void);

    77   // Print the statistics for all the lists in the tree.  Also may

    78   // print out summaries.

    79   void       print_dict_census(outputStream* st) const;

    80 };

    81 

    82 class LinearAllocBlock {

    83  public:

    84   LinearAllocBlock() : _ptr(0), _word_size(0), _refillSize(0),

    85     _allocation_size_limit(0) {}

    86   void set(HeapWord* ptr, size_t word_size, size_t refill_size,

    87     size_t allocation_size_limit) {

    88     _ptr = ptr;

    89     _word_size = word_size;

    90     _refillSize = refill_size;

    91     _allocation_size_limit = allocation_size_limit;

    92   }

    93   HeapWord* _ptr;

    94   size_t    _word_size;

    95   size_t    _refillSize;

    96   size_t    _allocation_size_limit;  // Largest size that will be allocated

    97 

    98   void print_on(outputStream* st) const;

    99 };

   100 

   101 // Concrete subclass of CompactibleSpace that implements

   102 // a free list space, such as used in the concurrent mark sweep

   103 // generation.

   104 

   105 class CompactibleFreeListSpace: public CompactibleSpace {

   106   friend class VMStructs;

   107   friend class ConcurrentMarkSweepGeneration;

   108   friend class CMSCollector;

   109   // Local alloc buffer for promotion into this space.

   110   friend class CompactibleFreeListSpaceLAB;

   111   // Allow scan_and_* functions to call (private) overrides of the auxiliary functions on this class

   112   template <typename SpaceType>

   113   friend void CompactibleSpace::scan_and_adjust_pointers(SpaceType* space);

   114   template <typename SpaceType>

   115   friend void CompactibleSpace::scan_and_compact(SpaceType* space);

   116   template <typename SpaceType>

   117   friend void CompactibleSpace::verify_up_to_first_dead(SpaceType* space);

   118   template <typename SpaceType>

   119   friend void CompactibleSpace::scan_and_forward(SpaceType* space, CompactPoint* cp);

   120 

   121   // "Size" of chunks of work (executed during parallel remark phases

   122   // of CMS collection); this probably belongs in CMSCollector, although

   123   // it's cached here because it's used in

   124   // initialize_sequential_subtasks_for_rescan() which modifies

   125   // par_seq_tasks which also lives in Space. XXX

   126   const size_t _rescan_task_size;

   127   const size_t _marking_task_size;

   128 

   129   // Yet another sequential tasks done structure. This supports

   130   // CMS GC, where we have threads dynamically

   131   // claiming sub-tasks from a larger parallel task.

   132   SequentialSubTasksDone _conc_par_seq_tasks;

   133 

   134   BlockOffsetArrayNonContigSpace _bt;

   135 

   136   CMSCollector* _collector;

   137   ConcurrentMarkSweepGeneration* _old_gen;

   138 

   139   // Data structures for free blocks (used during allocation/sweeping)

   140 

   141   // Allocation is done linearly from two different blocks depending on

   142   // whether the request is small or large, in an effort to reduce

   143   // fragmentation. We assume that any locking for allocation is done

   144   // by the containing generation. Thus, none of the methods in this

   145   // space are re-entrant.

   146   enum SomeConstants {

   147     SmallForLinearAlloc = 16,        // size < this then use _sLAB

   148     SmallForDictionary  = 257,       // size < this then use _indexedFreeList

   149     IndexSetSize        = SmallForDictionary  // keep this odd-sized

   150   };

   151   static size_t IndexSetStart;

   152   static size_t IndexSetStride;

   153   static size_t _min_chunk_size_in_bytes;

   154 

   155  private:

   156   enum FitStrategyOptions {

   157     FreeBlockStrategyNone = 0,

   158     FreeBlockBestFitFirst

   159   };

   160 

   161   PromotionInfo _promoInfo;

   162 

   163   // Helps to impose a global total order on freelistLock ranks;

   164   // assumes that CFLSpace's are allocated in global total order

   165   static int   _lockRank;

   166 

   167   // A lock protecting the free lists and free blocks;

   168   // mutable because of ubiquity of locking even for otherwise const methods

   169   mutable Mutex _freelistLock;

   170 

   171   // Locking verifier convenience function

   172   void assert_locked() const PRODUCT_RETURN;

   173   void assert_locked(const Mutex* lock) const PRODUCT_RETURN;

   174 

   175   // Linear allocation blocks

   176   LinearAllocBlock _smallLinearAllocBlock;

   177 

   178   AFLBinaryTreeDictionary* _dictionary;    // Pointer to dictionary for large size blocks

   179 

   180   // Indexed array for small size blocks

   181   AdaptiveFreeList<FreeChunk> _indexedFreeList[IndexSetSize];

   182 

   183   // Allocation strategy

   184   bool _fitStrategy;  // Use best fit strategy

   185 

   186   // This is an address close to the largest free chunk in the heap.

   187   // It is currently assumed to be at the end of the heap.  Free

   188   // chunks with addresses greater than nearLargestChunk are coalesced

   189   // in an effort to maintain a large chunk at the end of the heap.

   190   HeapWord*  _nearLargestChunk;

   191 

   192   // Used to keep track of limit of sweep for the space

   193   HeapWord* _sweep_limit;

   194 

   195   // Stable value of used().

   196   size_t _used_stable;

   197 

   198   // Used to make the young collector update the mod union table

   199   MemRegionClosure* _preconsumptionDirtyCardClosure;

   200 

   201   // Support for compacting cms

   202   HeapWord* cross_threshold(HeapWord* start, HeapWord* end);

   203   HeapWord* forward(oop q, size_t size, CompactPoint* cp, HeapWord* compact_top);

   204 

   205   // Initialization helpers.

   206   void initializeIndexedFreeListArray();

   207 

   208   // Extra stuff to manage promotion parallelism.

   209 

   210   // A lock protecting the dictionary during par promotion allocation.

   211   mutable Mutex _parDictionaryAllocLock;

   212   Mutex* parDictionaryAllocLock() const { return &_parDictionaryAllocLock; }

   213 

   214   // Locks protecting the exact lists during par promotion allocation.

   215   Mutex* _indexedFreeListParLocks[IndexSetSize];

   216 

   217   // Attempt to obtain up to "n" blocks of the size "word_sz" (which is

   218   // required to be smaller than "IndexSetSize".)  If successful,

   219   // adds them to "fl", which is required to be an empty free list.

   220   // If the count of "fl" is negative, it's absolute value indicates a

   221   // number of free chunks that had been previously "borrowed" from global

   222   // list of size "word_sz", and must now be decremented.

   223   void par_get_chunk_of_blocks(size_t word_sz, size_t n, AdaptiveFreeList<FreeChunk>* fl);

   224 

   225   // Used by par_get_chunk_of_blocks() for the chunks from the

   226   // indexed_free_lists.

   227   bool par_get_chunk_of_blocks_IFL(size_t word_sz, size_t n, AdaptiveFreeList<FreeChunk>* fl);

   228 

   229   // Used by par_get_chunk_of_blocks_dictionary() to get a chunk

   230   // evenly splittable into "n" "word_sz" chunks.  Returns that

   231   // evenly splittable chunk.  May split a larger chunk to get the

   232   // evenly splittable chunk.

   233   FreeChunk* get_n_way_chunk_to_split(size_t word_sz, size_t n);

   234 

   235   // Used by par_get_chunk_of_blocks() for the chunks from the

   236   // dictionary.

   237   void par_get_chunk_of_blocks_dictionary(size_t word_sz, size_t n, AdaptiveFreeList<FreeChunk>* fl);

   238 

   239   // Allocation helper functions

   240   // Allocate using a strategy that takes from the indexed free lists

   241   // first.  This allocation strategy assumes a companion sweeping

   242   // strategy that attempts to keep the needed number of chunks in each

   243   // indexed free lists.

   244   HeapWord* allocate_adaptive_freelists(size_t size);

   245 

   246   // Gets a chunk from the linear allocation block (LinAB).  If there

   247   // is not enough space in the LinAB, refills it.

   248   HeapWord*  getChunkFromLinearAllocBlock(LinearAllocBlock* blk, size_t size);

   249   HeapWord*  getChunkFromSmallLinearAllocBlock(size_t size);

   250   // Get a chunk from the space remaining in the linear allocation block.  Do

   251   // not attempt to refill if the space is not available, return NULL.  Do the

   252   // repairs on the linear allocation block as appropriate.

   253   HeapWord*  getChunkFromLinearAllocBlockRemainder(LinearAllocBlock* blk, size_t size);

   254   inline HeapWord*  getChunkFromSmallLinearAllocBlockRemainder(size_t size);

   255 

   256   // Helper function for getChunkFromIndexedFreeList.

   257   // Replenish the indexed free list for this "size".  Do not take from an

   258   // underpopulated size.

   259   FreeChunk*  getChunkFromIndexedFreeListHelper(size_t size, bool replenish = true);

   260 

   261   // Get a chunk from the indexed free list.  If the indexed free list

   262   // does not have a free chunk, try to replenish the indexed free list

   263   // then get the free chunk from the replenished indexed free list.

   264   inline FreeChunk* getChunkFromIndexedFreeList(size_t size);

   265 

   266   // The returned chunk may be larger than requested (or null).

   267   FreeChunk* getChunkFromDictionary(size_t size);

   268   // The returned chunk is the exact size requested (or null).

   269   FreeChunk* getChunkFromDictionaryExact(size_t size);

   270 

   271   // Find a chunk in the indexed free list that is the best

   272   // fit for size "numWords".

   273   FreeChunk* bestFitSmall(size_t numWords);

   274   // For free list "fl" of chunks of size > numWords,

   275   // remove a chunk, split off a chunk of size numWords

   276   // and return it.  The split off remainder is returned to

   277   // the free lists.  The old name for getFromListGreater

   278   // was lookInListGreater.

   279   FreeChunk* getFromListGreater(AdaptiveFreeList<FreeChunk>* fl, size_t numWords);

   280   // Get a chunk in the indexed free list or dictionary,

   281   // by considering a larger chunk and splitting it.

   282   FreeChunk* getChunkFromGreater(size_t numWords);

   283   //  Verify that the given chunk is in the indexed free lists.

   284   bool verifyChunkInIndexedFreeLists(FreeChunk* fc) const;

   285   // Remove the specified chunk from the indexed free lists.

   286   void       removeChunkFromIndexedFreeList(FreeChunk* fc);

   287   // Remove the specified chunk from the dictionary.

   288   void       removeChunkFromDictionary(FreeChunk* fc);

   289   // Split a free chunk into a smaller free chunk of size "new_size".

   290   // Return the smaller free chunk and return the remainder to the

   291   // free lists.

   292   FreeChunk* splitChunkAndReturnRemainder(FreeChunk* chunk, size_t new_size);

   293   // Add a chunk to the free lists.

   294   void       addChunkToFreeLists(HeapWord* chunk, size_t size);

   295   // Add a chunk to the free lists, preferring to suffix it

   296   // to the last free chunk at end of space if possible, and

   297   // updating the block census stats as well as block offset table.

   298   // Take any locks as appropriate if we are multithreaded.

   299   void       addChunkToFreeListsAtEndRecordingStats(HeapWord* chunk, size_t size);

   300   // Add a free chunk to the indexed free lists.

   301   void       returnChunkToFreeList(FreeChunk* chunk);

   302   // Add a free chunk to the dictionary.

   303   void       returnChunkToDictionary(FreeChunk* chunk);

   304 

   305   // Functions for maintaining the linear allocation buffers (LinAB).

   306   // Repairing a linear allocation block refers to operations

   307   // performed on the remainder of a LinAB after an allocation

   308   // has been made from it.

   309   void       repairLinearAllocationBlocks();

   310   void       repairLinearAllocBlock(LinearAllocBlock* blk);

   311   void       refillLinearAllocBlock(LinearAllocBlock* blk);

   312   void       refillLinearAllocBlockIfNeeded(LinearAllocBlock* blk);

   313   void       refillLinearAllocBlocksIfNeeded();

   314 

   315   void       verify_objects_initialized() const;

   316 

   317   // Statistics reporting helper functions

   318   void       reportFreeListStatistics(const char* title) const;

   319   void       reportIndexedFreeListStatistics(outputStream* st) const;

   320   size_t     maxChunkSizeInIndexedFreeLists() const;

   321   size_t     numFreeBlocksInIndexedFreeLists() const;

   322   // Accessor

   323   HeapWord* unallocated_block() const {

   324     if (BlockOffsetArrayUseUnallocatedBlock) {

   325       HeapWord* ub = _bt.unallocated_block();

   326       assert(ub >= bottom() &&

   327              ub <= end(), "space invariant");

   328       return ub;

   329     } else {

   330       return end();

   331     }

   332   }

   333   void freed(HeapWord* start, size_t size) {

   334     _bt.freed(start, size);

   335   }

   336 

   337   // Auxiliary functions for scan_and_{forward,adjust_pointers,compact} support.

   338   // See comments for CompactibleSpace for more information.

   339   inline HeapWord* scan_limit() const {

   340     return end();

   341   }

   342 

   343   inline bool scanned_block_is_obj(const HeapWord* addr) const {

   344     return CompactibleFreeListSpace::block_is_obj(addr); // Avoid virtual call

   345   }

   346 

   347   inline size_t scanned_block_size(const HeapWord* addr) const {

   348     return CompactibleFreeListSpace::block_size(addr); // Avoid virtual call

   349   }

   350 

   351   inline size_t adjust_obj_size(size_t size) const {

   352     return adjustObjectSize(size);

   353   }

   354 

   355   inline size_t obj_size(const HeapWord* addr) const;

   356 

   357  protected:

   358   // Reset the indexed free list to its initial empty condition.

   359   void resetIndexedFreeListArray();

   360   // Reset to an initial state with a single free block described

   361   // by the MemRegion parameter.

   362   void reset(MemRegion mr);

   363   // Return the total number of words in the indexed free lists.

   364   size_t     totalSizeInIndexedFreeLists() const;

   365 

   366  public:

   367   // Constructor

   368   CompactibleFreeListSpace(BlockOffsetSharedArray* bs, MemRegion mr);

   369   // Accessors

   370   bool bestFitFirst() { return _fitStrategy == FreeBlockBestFitFirst; }

   371   AFLBinaryTreeDictionary* dictionary() const { return _dictionary; }

   372   HeapWord* nearLargestChunk() const { return _nearLargestChunk; }

   373   void set_nearLargestChunk(HeapWord* v) { _nearLargestChunk = v; }

   374 

   375   // Set CMS global values.

   376   static void set_cms_values();

   377 

   378   // Return the free chunk at the end of the space.  If no such

   379   // chunk exists, return NULL.

   380   FreeChunk* find_chunk_at_end();

   381 

   382   void set_collector(CMSCollector* collector) { _collector = collector; }

   383 

   384   // Support for parallelization of rescan and marking.

   385   const size_t rescan_task_size()  const { return _rescan_task_size;  }

   386   const size_t marking_task_size() const { return _marking_task_size; }

   387   // Return ergonomic max size for CMSRescanMultiple and CMSConcMarkMultiple.

   388   const size_t max_flag_size_for_task_size() const;

   389   SequentialSubTasksDone* conc_par_seq_tasks() {return &_conc_par_seq_tasks; }

   390   void initialize_sequential_subtasks_for_rescan(int n_threads);

   391   void initialize_sequential_subtasks_for_marking(int n_threads,

   392          HeapWord* low = NULL);

   393 

   394   virtual MemRegionClosure* preconsumptionDirtyCardClosure() const {

   395     return _preconsumptionDirtyCardClosure;

   396   }

   397 

   398   void setPreconsumptionDirtyCardClosure(MemRegionClosure* cl) {

   399     _preconsumptionDirtyCardClosure = cl;

   400   }

   401 

   402   // Space enquiries

   403   size_t used() const;

   404   size_t free() const;

   405   size_t max_alloc_in_words() const;

   406   // XXX: should have a less conservative used_region() than that of

   407   // Space; we could consider keeping track of highest allocated

   408   // address and correcting that at each sweep, as the sweeper

   409   // goes through the entire allocated part of the generation. We

   410   // could also use that information to keep the sweeper from

   411   // sweeping more than is necessary. The allocator and sweeper will

   412   // of course need to synchronize on this, since the sweeper will

   413   // try to bump down the address and the allocator will try to bump it up.

   414   // For now, however, we'll just use the default used_region()

   415   // which overestimates the region by returning the entire

   416   // committed region (this is safe, but inefficient).

   417 

   418   // Returns monotonically increasing stable used space bytes for CMS.

   419   // This is required for jstat and other memory monitoring tools

   420   // that might otherwise see inconsistent used space values during a garbage

   421   // collection, promotion or allocation into compactibleFreeListSpace.

   422   // The value returned by this function might be smaller than the

   423   // actual value.

   424   size_t used_stable() const;

   425   // Recalculate and cache the current stable used() value. Only to be called

   426   // in places where we can be sure that the result is stable.

   427   void recalculate_used_stable();

   428 

   429   // Returns a subregion of the space containing all the objects in

   430   // the space.

   431   MemRegion used_region() const {

   432     return MemRegion(bottom(),

   433                      BlockOffsetArrayUseUnallocatedBlock ?

   434                      unallocated_block() : end());

   435   }

   436 

   437   virtual bool is_free_block(const HeapWord* p) const;

   438 

   439   // Resizing support

   440   void set_end(HeapWord* value);  // override

   441 

   442   // Never mangle CompactibleFreeListSpace

   443   void mangle_unused_area() {}

   444   void mangle_unused_area_complete() {}

   445 

   446   // Mutual exclusion support

   447   Mutex* freelistLock() const { return &_freelistLock; }

   448 

   449   // Iteration support

   450   void oop_iterate(OopIterateClosure* cl);

   451 

   452   void object_iterate(ObjectClosure* blk);

   453   // Apply the closure to each object in the space whose references

   454   // point to objects in the heap.  The usage of CompactibleFreeListSpace

   455   // by the ConcurrentMarkSweepGeneration for concurrent GC's allows

   456   // objects in the space with references to objects that are no longer

   457   // valid.  For example, an object may reference another object

   458   // that has already been sweep up (collected).  This method uses

   459   // obj_is_alive() to determine whether it is safe to iterate of

   460   // an object.

   461   void safe_object_iterate(ObjectClosure* blk);

   462 

   463   // Iterate over all objects that intersect with mr, calling "cl->do_object"

   464   // on each.  There is an exception to this: if this closure has already

   465   // been invoked on an object, it may skip such objects in some cases.  This is

   466   // Most likely to happen in an "upwards" (ascending address) iteration of

   467   // MemRegions.

   468   void object_iterate_mem(MemRegion mr, UpwardsObjectClosure* cl);

   469 

   470   // Requires that "mr" be entirely within the space.

   471   // Apply "cl->do_object" to all objects that intersect with "mr".

   472   // If the iteration encounters an unparseable portion of the region,

   473   // terminate the iteration and return the address of the start of the

   474   // subregion that isn't done.  Return of "NULL" indicates that the

   475   // iteration completed.

   476   HeapWord* object_iterate_careful_m(MemRegion mr,

   477                                      ObjectClosureCareful* cl);

   478 

   479   // Override: provides a DCTO_CL specific to this kind of space.

   480   DirtyCardToOopClosure* new_dcto_cl(OopIterateClosure* cl,

   481                                      CardTable::PrecisionStyle precision,

   482                                      HeapWord* boundary,

   483                                      bool parallel);

   484 

   485   void blk_iterate(BlkClosure* cl);

   486   void blk_iterate_careful(BlkClosureCareful* cl);

   487   HeapWord* block_start_const(const void* p) const;

   488   HeapWord* block_start_careful(const void* p) const;

   489   size_t block_size(const HeapWord* p) const;

   490   size_t block_size_no_stall(HeapWord* p, const CMSCollector* c) const;

   491   bool block_is_obj(const HeapWord* p) const;

   492   bool obj_is_alive(const HeapWord* p) const;

   493   size_t block_size_nopar(const HeapWord* p) const;

   494   bool block_is_obj_nopar(const HeapWord* p) const;

   495 

   496   // Iteration support for promotion

   497   void save_marks();

   498   bool no_allocs_since_save_marks();

   499 

   500   // Iteration support for sweeping

   501   void save_sweep_limit() {

   502     _sweep_limit = BlockOffsetArrayUseUnallocatedBlock ?

   503                    unallocated_block() : end();

   504     log_develop_trace(gc, sweep)(">>>>> Saving sweep limit " PTR_FORMAT

   505                                  "  for space [" PTR_FORMAT "," PTR_FORMAT ") <<<<<<",

   506                                  p2i(_sweep_limit), p2i(bottom()), p2i(end()));

   507   }

   508   NOT_PRODUCT(

   509     void clear_sweep_limit() { _sweep_limit = NULL; }

   510   )

   511   HeapWord* sweep_limit() { return _sweep_limit; }

   512 

   513   // Apply "blk->do_oop" to the addresses of all reference fields in objects

   514   // promoted into this generation since the most recent save_marks() call.

   515   // Fields in objects allocated by applications of the closure

   516   // *are* included in the iteration. Thus, when the iteration completes

   517   // there should be no further such objects remaining.

   518   template <typename OopClosureType>

   519   void oop_since_save_marks_iterate(OopClosureType* blk);

   520 

   521   // Allocation support

   522   HeapWord* allocate(size_t size);

   523   HeapWord* par_allocate(size_t size);

   524 

   525   oop       promote(oop obj, size_t obj_size);

   526   void      gc_prologue();

   527   void      gc_epilogue();

   528 

   529   // This call is used by a containing CMS generation / collector

   530   // to inform the CFLS space that a sweep has been completed

   531   // and that the space can do any related house-keeping functions.

   532   void      sweep_completed();

   533 

   534   // For an object in this space, the mark-word's two

   535   // LSB's having the value [11] indicates that it has been

   536   // promoted since the most recent call to save_marks() on

   537   // this generation and has not subsequently been iterated

   538   // over (using oop_since_save_marks_iterate() above).

   539   // This property holds only for single-threaded collections,

   540   // and is typically used for Cheney scans; for MT scavenges,

   541   // the property holds for all objects promoted during that

   542   // scavenge for the duration of the scavenge and is used

   543   // by card-scanning to avoid scanning objects (being) promoted

   544   // during that scavenge.

   545   bool obj_allocated_since_save_marks(const oop obj) const {

   546     assert(is_in_reserved(obj), "Wrong space?");

   547     return ((PromotedObject*)obj)->hasPromotedMark();

   548   }

   549 

   550   // A worst-case estimate of the space required (in HeapWords) to expand the

   551   // heap when promoting an obj of size obj_size.

   552   size_t expansionSpaceRequired(size_t obj_size) const;

   553 

   554   FreeChunk* allocateScratch(size_t size);

   555 

   556   // Returns true if either the small or large linear allocation buffer is empty.

   557   bool       linearAllocationWouldFail() const;

   558 

   559   // Adjust the chunk for the minimum size.  This version is called in

   560   // most cases in CompactibleFreeListSpace methods.

   561   inline static size_t adjustObjectSize(size_t size) {

   562     return align_object_size(MAX2(size, (size_t)MinChunkSize));

   563   }

   564   // This is a virtual version of adjustObjectSize() that is called

   565   // only occasionally when the compaction space changes and the type

   566   // of the new compaction space is is only known to be CompactibleSpace.

   567   size_t adjust_object_size_v(size_t size) const {

   568     return adjustObjectSize(size);

   569   }

   570   // Minimum size of a free block.

   571   virtual size_t minimum_free_block_size() const { return MinChunkSize; }

   572   void      removeFreeChunkFromFreeLists(FreeChunk* chunk);

   573   void      addChunkAndRepairOffsetTable(HeapWord* chunk, size_t size,

   574               bool coalesced);

   575 

   576   // Support for compaction.

   577   void prepare_for_compaction(CompactPoint* cp);

   578   void adjust_pointers();

   579   void compact();

   580   // Reset the space to reflect the fact that a compaction of the

   581   // space has been done.

   582   virtual void reset_after_compaction();

   583 

   584   // Debugging support.

   585   void print()                            const;

   586   void print_on(outputStream* st)         const;

   587   void prepare_for_verify();

   588   void verify()                           const;

   589   void verifyFreeLists()                  const PRODUCT_RETURN;

   590   void verifyIndexedFreeLists()           const;

   591   void verifyIndexedFreeList(size_t size) const;

   592   // Verify that the given chunk is in the free lists:

   593   // i.e. either the binary tree dictionary, the indexed free lists

   594   // or the linear allocation block.

   595   bool verify_chunk_in_free_list(FreeChunk* fc) const;

   596   // Verify that the given chunk is the linear allocation block.

   597   bool verify_chunk_is_linear_alloc_block(FreeChunk* fc) const;

   598   // Do some basic checks on the the free lists.

   599   void check_free_list_consistency()      const PRODUCT_RETURN;

   600 

   601   // Printing support

   602   void dump_at_safepoint_with_locks(CMSCollector* c, outputStream* st);

   603   void print_indexed_free_lists(outputStream* st) const;

   604   void print_dictionary_free_lists(outputStream* st) const;

   605   void print_promo_info_blocks(outputStream* st) const;

   606 

   607   NOT_PRODUCT (

   608     void initializeIndexedFreeListArrayReturnedBytes();

   609     size_t sumIndexedFreeListArrayReturnedBytes();

   610     // Return the total number of chunks in the indexed free lists.

   611     size_t totalCountInIndexedFreeLists() const;

   612     // Return the total number of chunks in the space.

   613     size_t totalCount();

   614   )

   615 

   616   // The census consists of counts of the quantities such as

   617   // the current count of the free chunks, number of chunks

   618   // created as a result of the split of a larger chunk or

   619   // coalescing of smaller chucks, etc.  The counts in the

   620   // census is used to make decisions on splitting and

   621   // coalescing of chunks during the sweep of garbage.

   622 

   623   // Print the statistics for the free lists.

   624   void printFLCensus(size_t sweep_count) const;

   625 

   626   // Statistics functions

   627   // Initialize census for lists before the sweep.

   628   void beginSweepFLCensus(float inter_sweep_current,

   629                           float inter_sweep_estimate,

   630                           float intra_sweep_estimate);

   631   // Set the surplus for each of the free lists.

   632   void setFLSurplus();

   633   // Set the hint for each of the free lists.

   634   void setFLHints();

   635   // Clear the census for each of the free lists.

   636   void clearFLCensus();

   637   // Perform functions for the census after the end of the sweep.

   638   void endSweepFLCensus(size_t sweep_count);

   639   // Return true if the count of free chunks is greater

   640   // than the desired number of free chunks.

   641   bool coalOverPopulated(size_t size);

   642 

   643 // Record (for each size):

   644 //

   645 //   split-births = #chunks added due to splits in (prev-sweep-end,

   646 //      this-sweep-start)

   647 //   split-deaths = #chunks removed for splits in (prev-sweep-end,

   648 //      this-sweep-start)

   649 //   num-curr     = #chunks at start of this sweep

   650 //   num-prev     = #chunks at end of previous sweep

   651 //

   652 // The above are quantities that are measured. Now define:

   653 //

   654 //   num-desired := num-prev + split-births - split-deaths - num-curr

   655 //

   656 // Roughly, num-prev + split-births is the supply,

   657 // split-deaths is demand due to other sizes

   658 // and num-curr is what we have left.

   659 //

   660 // Thus, num-desired is roughly speaking the "legitimate demand"

   661 // for blocks of this size and what we are striving to reach at the

   662 // end of the current sweep.

   663 //

   664 // For a given list, let num-len be its current population.

   665 // Define, for a free list of a given size:

   666 //

   667 //   coal-overpopulated := num-len >= num-desired * coal-surplus

   668 // (coal-surplus is set to 1.05, i.e. we allow a little slop when

   669 // coalescing -- we do not coalesce unless we think that the current

   670 // supply has exceeded the estimated demand by more than 5%).

   671 //

   672 // For the set of sizes in the binary tree, which is neither dense nor

   673 // closed, it may be the case that for a particular size we have never

   674 // had, or do not now have, or did not have at the previous sweep,

   675 // chunks of that size. We need to extend the definition of

   676 // coal-overpopulated to such sizes as well:

   677 //

   678 //   For a chunk in/not in the binary tree, extend coal-overpopulated

   679 //   defined above to include all sizes as follows:

   680 //

   681 //   . a size that is non-existent is coal-overpopulated

   682 //   . a size that has a num-desired <= 0 as defined above is

   683 //     coal-overpopulated.

   684 //

   685 // Also define, for a chunk heap-offset C and mountain heap-offset M:

   686 //

   687 //   close-to-mountain := C >= 0.99 * M

   688 //

   689 // Now, the coalescing strategy is:

   690 //

   691 //    Coalesce left-hand chunk with right-hand chunk if and

   692 //    only if:

   693 //

   694 //      EITHER

   695 //        . left-hand chunk is of a size that is coal-overpopulated

   696 //      OR

   697 //        . right-hand chunk is close-to-mountain

   698   void smallCoalBirth(size_t size);

   699   void smallCoalDeath(size_t size);

   700   void coalBirth(size_t size);

   701   void coalDeath(size_t size);

   702   void smallSplitBirth(size_t size);

   703   void smallSplitDeath(size_t size);

   704   void split_birth(size_t size);

   705   void splitDeath(size_t size);

   706   void split(size_t from, size_t to1);

   707 

   708   double flsFrag() const;

   709 };

   710 

   711 // A parallel-GC-thread-local allocation buffer for allocation into a

   712 // CompactibleFreeListSpace.

   713 class CompactibleFreeListSpaceLAB : public CHeapObj<mtGC> {

   714   // The space that this buffer allocates into.

   715   CompactibleFreeListSpace* _cfls;

   716 

   717   // Our local free lists.

   718   AdaptiveFreeList<FreeChunk> _indexedFreeList[CompactibleFreeListSpace::IndexSetSize];

   719 

   720   // Initialized from a command-line arg.

   721 

   722   // Allocation statistics in support of dynamic adjustment of

   723   // #blocks to claim per get_from_global_pool() call below.

   724   static AdaptiveWeightedAverage

   725                  _blocks_to_claim  [CompactibleFreeListSpace::IndexSetSize];

   726   static size_t _global_num_blocks [CompactibleFreeListSpace::IndexSetSize];

   727   static uint   _global_num_workers[CompactibleFreeListSpace::IndexSetSize];

   728   size_t        _num_blocks        [CompactibleFreeListSpace::IndexSetSize];

   729 

   730   // Internal work method

   731   void get_from_global_pool(size_t word_sz, AdaptiveFreeList<FreeChunk>* fl);

   732 

   733 public:

   734   static const int _default_dynamic_old_plab_size = 16;

   735   static const int _default_static_old_plab_size  = 50;

   736 

   737   CompactibleFreeListSpaceLAB(CompactibleFreeListSpace* cfls);

   738 

   739   // Allocate and return a block of the given size, or else return NULL.

   740   HeapWord* alloc(size_t word_sz);

   741 

   742   // Return any unused portions of the buffer to the global pool.

   743   void retire(int tid);

   744 

   745   // Dynamic OldPLABSize sizing

   746   static void compute_desired_plab_size();

   747   // When the settings are modified from default static initialization

   748   static void modify_initialization(size_t n, unsigned wt);

   749 };

   750 

   751 size_t PromotionInfo::refillSize() const {

   752   const size_t CMSSpoolBlockSize = 256;

   753   const size_t sz = heap_word_size(sizeof(SpoolBlock) + sizeof(markWord)

   754                                    * CMSSpoolBlockSize);

   755   return CompactibleFreeListSpace::adjustObjectSize(sz);

   756 }

   757 

   758 #endif // SHARE_GC_CMS_COMPACTIBLEFREELISTSPACE_HPP